In the past, a number of control circuits have been developed to operate gas filled flash lamps in a periodic and controlled manner. With such circuits, flash lamps are caused to provide light in response to an electrical discharge through the lamp produced upon receipt of a control signal from a flash control unit. One effective prior art circuit is illustrated by U.S. Pat. No. 3,543,087 to G. P. Saiger et al. which discloses a circuit for controlling electric discharges through a flash lamp at a preselected rate and preselected phase with respect to an input from an alternating voltage source. The circuit includes a phase control system which provides halfwave phase control for determining the preselected phase relation of electrical discharges through a flash lamp, as well as flash rate control which provides a firing or trigger signal to the flash lamp to effect electrical discharge.
The Saiger et al. patent illustrates a single control circuit for a single flash lamp, and although such devices have found utility in various fields of use for a multitude of purposes, there has recently arisen a great demand for systems including a large number of lamps which are controlled from a single controller. Multiple lamp systems are particularly desirable for stage lighting, and for producing various types of theatrical effects, and consequently the ability to control both the phase and timing of a large number of flash lamps from a single controller would be most desirable.
Relatively sophisticated optical systems have been developed to provide an infinite variety of lighting effects with multiple lamps of various types under the control of a central processor. Examples of such prior multiple lamp systems are illustrated by U.S. Pat. No. 4,262,338 to J. J. Gaudio, Jr., Pat. No. 4,392,187 to J. M. Bornhorst, and Pat. No. 4,635,052 to N. Aoike et al. As will be noted from these patents, the prior multiple lamp display systems disclosed normally include a relatively complex central controller which processes control signals to fire selected ones of a plurality of remote lamps. For example, the Aoike et al. patent shows a central controller which provides signals determinative of both the duty cycle and intensity of remote lamps, and the remote lamp circuit primarily contains only a discharge lamp and a high frequency generator, such as a generator including two thyristor inverters.
In the display system illustrated by the Gaudio, Jr. patent, lamp timing sychronization is determined by a central processor unit which generates interrupts at one or a plurality of intervals throughout each half cycle of an external power wave form. To achieve such interrupts, a conventional zero crossing detector detects the beginning of each period or half cycle of external power and resets counters with each zero crossing of a rectified half cycle of the input power signal. Here again, all control of multiple lamps is achieved from a complex central processor.
With multiple lamp systems, heat becomes a problem if an individual lamp is repetitively energized over a short period of time from a central controller. In an attempt to alleviate this heat problem, multiple lamp systems are generally supplied with cooling fans, as illustrated b the Bornhorst patent.